Skating, particularly in-line skating, is becoming increasingly popular. In-line skates generally include wheels fastened in tandem to a skate boot. The wheels typically include a hub made of rigid plastic material. A tire made of synthetic plastic material is typically molded about the periphery of the hub. Examples of in-line skates and hubs are shown in U.S. Design Pat. Nos. Des. 339,320; Des. 330,884; and Des. 330,883.
As shown in the above-referenced prior art patents, prior art skate hubs typically have a generally cylindrical core. Extending radially outward from the midpoint of the core is a protrusion. A plurality of holes are formed through the protrusion with the holes being circumferentially spaced about the axis of the core. A tire, typically made of urethane, is molded around the periphery of the hub. During the molding process, urethane flows into the holes formed through the protrusion. As a result of the molding process, the urethane material of the tire is securely molded to the hub.
EP Publication No. 0 642 814 A1 discloses a wheel including a central hub having a plurality of spokes. The wheel also includes a tire which may partially or fully affect the interspace between the spokes and the central hub. The wheel is configured to allow a user to preset the optimum degree of rigidity according to his/her individual technical requirements and according to the type of surface on which the wheel is to be used.
U.S. Pat. No. 5,310,250 discloses a skate wheel including a hub having a core and a central rail positioned at a mid-region of the core. The central rail is connected to the core by a plurality of staggered inner support members. A tire is mounted on the core and formed over the central rail.
At times, a wheel may experience substantial side forces on the hub and tire. The side forces can cause the molded urethane tire to break away from the hub (referred to as de-lamination). Furthermore, as the tire wears, the diameter of the wheel decreases. Therefore, the distance between the outer periphery of the tire and outer periphery of the central protrusion of the hub progressively decreases during wear of the tire. As this distance gradually decreases, the performance or bounce of the wheel also decreases.
Certain improvements to skate wheels have been developed to overcome the above-identified problems. For example, in some skate wheels, the central protrusion of the hub core has been replaced with a pair of anchors or rings that extend around the circumference of the hub core. The anchors are provided in spaced-apart relation to define a material receiving volume therebetween. A urethane tire is molded over the pair of anchors and at least partially fills the material-receiving volume formed between the anchors.
The above-identified hub configuration is typically manufactured via an injection molding process. Generally, a four-piece mold is used to define an inner volume that coincides with the shape of the hub. To form the hub, plastic material is injected into the inner volume defined by the mold. After the plastic material has cooled and hardened, the formed hub can be removed from the mold.